Device for managing the kinematics of a seat with mobile seating element

ABSTRACT

The method of managing the kinematics of a seat ( 10 ) includes at least three seat elements ( 16, 18, 22 ) able to move with respect to each other and at least two actuators ( 26, 27 ) for moving the three elements ( 16, 18, 22 ) with respect to each other. When a first actuator ( 27 ) is actuated in at least one direction, it includes a step of actuating a second actuator ( 26 ) first of all in a given direction and then in the opposite direction.

The present invention concerns a method for managing the kinematics of aseat having at least three seat elements able to move with respect toeach other and at least two actuators for moving the three elements withrespect to each other.

This method applies notably to vehicle seats able to be used notably inaircraft for transporting passengers.

These seats generally have a squab which can be moved with respect tothe base. An inclinable back rest is articulated at one end of thesquab, whilst at its other end there is articulated a leg rest extendedby a movable foot rest.

Electrical actuators equip the seat, in order to move the differentelements thereof with respect to each other.

In some seats, the height of the squab can be modified by virtue of themovement possible between the squab and the base of the seat. Themovement can be effected by means of a specific actuator located betweenthe squab and the base. It can also result from the mechanical structureof the seat which mechanically connects the squab to another element ofthe seat, and for example its back rest. Thus, for example, when theseat back rest is moved to its upright position, the squab issimultaneously lowered.

In a seat equipped with such synchronism between the movements of theback rest and squab, it will be understood that, when the leg rest isessentially vertical and the foot rest is sufficiently brought out, thelowering of the squab during the movement of the back rest can cause thebottom end of the foot rest to come into contact notably with the floor,the foot rest/leg rest assembly being supported solely by the end of thesquab. When the squab is lowered, the foot rest/leg rest assembly isthen subjected to high mechanical stresses which may damage it.

Generally it will be understood that the effect of the movement of aseat element under the control of an actuator may cause damage to otherelements of the seat when the latter comes into contact with anobstacle.

The aim of the invention is to afford a solution to this problem byproposing a method of managing the kinematics of the seat preventing anelement of the seat driven by another element of the seat fromundergoing excessive mechanical stresses, when an actuator actingindirectly on it is actuated.

To this end, the object of the invention is a method of managing thekinematics of a seat of the aforementioned type, characterised in that,when a first actuator is actuated in at least one direction, it includesa step of actuating a second actuator first of all in one givendirection and then in the opposite direction.

According to particular embodiments, the method includes one or more ofthe following characteristics:

the actuation of the second actuator in the given direction is effectedfor a first predetermined duration;

the actuation of the second actuator in the opposite direction iseffected for a second predetermined duration;

the first and second predetermined durations are such that, according tothe speed of movement of the second actuator in the given direction andin the opposite direction, the movement travels in the two directionsare substantially identical;

before the step of actuating the second actuator in the said givendirection, it includes a step of measuring and storing the currentposition of the second actuator, and the actuation of the secondactuator in the said opposite direction is effected at most until thesecond actuator returns to the said stored position;

it includes a step of monitoring at least one variable characteristic ofthe force produced by the second actuator, during its use in the saidopposite direction, and a step of estimating at least one predeterminedevaluation criterion relating to the characteristic variable orvariables, and it includes a step of actuating the second actuatoraccording to a predefined actuation instruction, putting an end to itsmovement in the said opposite direction, when at least one of thepredetermined evaluation criteria is satisfied;

the said predetermined actuation instruction is an instruction chosenfrom the group consisting of the stoppage of the second actuator and thedriving of the second actuator in the said given direction; and

at least one variable characteristic of the force produced is a variablecharacteristic of the electric current consumed by the second actuatorchosen from the group consisting of the intensity consumed by theactuator and a derivative with respect to the time of the intensityconsumed by the actuator.

Another object of the invention is a seat including at least at leastthree seat elements movable with respect to each other and at least twoactuators for the movement of the three elements with respect to eachother, characterised in that it has means of actuating a first actuatorin one direction and automatic means of actuating a second actuatorfirst of all in a given direction and then in the opposite direction,when the first actuator is actuated in at least one direction.

According to particular embodiments, the seat has one or more of thefollowing characteristics:

it has:

a movable squab;

a back rest articulated on the squab;

a leg rest articulated on the squab; and

a foot rest mounted so as to be able to move with respect to the legrest; and

the first actuator is adapted for the conjoint movement of the back restand squab whilst providing the lowering of the seat when the back restis moved upright; and

the second actuator is adapted for the movement of the foot rest withrespect to the leg rest; and

it has:

a movable squab;

a back rest articulated on the squab; and

a leg rest articulated on the squab; and

the first actuator is adapted for the conjoint movement of the back restand squab whilst providing the lowering of the squab when the back restis moved upright; and

the second actuator is adapted for the movement of the leg rest withrespect to the squab.

The invention will be better understood from a reading of the followingdescription, given solely by way of example and made with reference tothe accompanying drawings, in which:

FIG. 1 is a schematic view of a vehicle seat according to the invention;

FIG. 2 is a flow diagram explaining the functioning of the seat throughthe implementation of the method of managing its kinematics according tothe invention; and

FIG. 3 is a flow diagram explaining the functioning of the seat duringan elementary phase of the management method, the function of this phasebeing to return the foot rest to its initial position.

The seat 10 depicted in FIG. 1 is a passenger seat for an aircraft. Thisseat is fixed to the floor 12 of the aircraft.

The seat 10 has a base 14 fixed to the floor 12 on which a substantiallyhorizontal squab 16 rests.

At one end of the squab there is articulated a back rest 18 able to movebetween a substantially vertical raised position and a substantiallyhorizontal folded-down position.

The squab 16 is mounted so as to be able to move with respect to thebase 14 in a vertical direction. A mechanism known per se lowers thesquab 16 when the back rest 18 is brought to its raised position andraises the squab 16 when the back rest 18 is returned to its folded-downposition.

At the other end of the squab 16 there is articulated a leg rest 20 ableto move between a substantially vertical folded-down position below thesquab 16 and a substantially horizontal extended position in line withthe squab 16. The leg rest is carried by the squab 16.

The seat 10 also has a foot rest 22 mounted so as to move slidably withrespect to the leg rest 20 in line with it.

The foot rest 22 is able to move between a retracted position within theleg rest 20 and an extended position in which it extends the latter andis practically completely extended.

A first electrical actuator 24 is mounted between the squab 16 and theleg rest 20 in order to provide a movement of the latter between itsfolded-down position and its extended position.

Likewise, a second actuator 26 is provided between the leg rest 20 andthe foot rest 22 in order to provide the movement of the foot restbetween its retracted position and its extended position.

A third actuator 27 is mounted between the squab 16 and the back rest 18in order to provide the movement of the back rest between its raisedposition and its folded-down position.

The three actuators function at constant speeds, which may be differentfrom one actuator to the other.

Each of the three actuators 24, 26 and 27 is supplied with electriccurrent from a central control unit 28. This control unit is connectedseparately to each of the actuators 24, 26 and 27 in order to providetheir independent control.

In addition, the seat has an arm rest 30, to which there is fixed acontrol keypad 32 affording independent control of the actuators 24, 26and 27 in order to cause their movement.

The unit 28 has a source 34 for supplying the actuators. This is formedfor example by a transformer connected to the general electrical supplysystem of the aircraft by adapted connection means.

For each actuator there is provided a supply interface 36, 38 and 39providing the supply of the actuators, respectively 24, 26 and 27, fromthe supply source 34. These interfaces provide the shaping of the supplycurrent for the actuators according to the required direction ofactuation.

The supply interfaces 36, 38 and 39 are controlled by an informationprocessing unit 40. This unit 40 is connected to the control keypad 32,in order to receive the control instructions from the passenger.

The information processing unit 40 has for example a microprocessor forimplementing an adapted program described later in the description.

The unit 40 also has a clock enabling the microprocessor to implementone or more timings in order to manage the duration of functioning ofthe different actuators.

Between the supply interfaces 36, 38, 39 and the actuators, respectively24, 26 and 27, there are disposed means denoted respectively 41, 42, 43,intended for monitoring variables characteristic of the electric currentconsumed by the actuators 24, 26 and 27 during their functioning. Thesemonitoring means are connected to the central information processingunit 40.

The variables characteristic of the electric current consumed by theactuators represent the force produced by the actuator in question.

For example, each of the monitoring means 41 to 43 is adapted todetermine the instantaneous intensity consumed by the associatedactuator, during its operating phase.

Finally, each actuator 24, 26 and 27 is equipped with one or moreposition sensors.

These sensors, designated by the reference 44, 46 and 47 respectivelyfor the actuators 24, 26 and 27, are connected to the informationprocessing unit 40. Thus the unit 40 is informed of the current positionof each actuator.

These sensors are formed for example by potentiometers or microcontactslocated between the fixed and movable parts of the actuators.

For the functioning of the seat, the information processing unit 40implements a program, known per se, adapted to control the supplyinterfaces 36, 38 and 39 so that these provide the supply to theactuators 24, 26 and 27 in one direction or the other by reversal of thedirection of current, as a function of the information received from theunit 40.

FIG. 2 shows the flow diagram of the program implemented by theinformation processing unit when the seat back rest is raised up to itsraised position.

Thus, when, at step 100, the passenger controls, by pressing on theappropriate key on the keypad 32, the raising up of the backrest, theactuator 27 is started up, at step 102, in order to actuate the backrest 18 to its raised position. It should be noted that, simultaneouslywith the raising up of the back rest, the squab 16 is progressivelylowered.

During the functioning of the actuator 27, a first test 104 is effectedin order to check that the control for raising up the back rest is stillvalid, that is to say that the user of the seat is still pressing thecorresponding key on the keypad. If such is not the case, the stoppageof the actuator 27 acting on the back rest is controlled at step 106.

If the control is still valid, it is checked, at step 108, that the backrest 18 has not reached its maximum raised position. This check iscarried out from information transmitted by the position sensor 47. Ifthe maximum position is reached, the stoppage of the back rest is alsocontrolled at step 106.

On the other hand, as long as the user maintains his back restraising-up control, and the back rest has not reached its maximumposition, the actuator 27 continues to function.

In parallel with the test carried out on the actuator 27 acting on theback rest and the squab, a step 110 of storing the position of the legrest is formed immediately after the actuator 27 is started up, at step102. This storage, carried out by the information processing unit 40,relates to the position value measured by the sensor 46 associated withthe actuator 26 allowing the movement of the foot rest 22 with respectto the leg rest 20.

At the following step 112, a timing of a predetermined duration T₁ istriggered. At step 114, the functioning of the actuator 26 controllingthe foot rest 22 is triggered. The actuator is started up in a firstdirection, causing a retraction of the foot rest 22 and thus a reductionin the total length of the assembly formed by the leg rest 20 and thefoot rest 22.

A set of tests is then carried out in a loop in order to determinewhether the functioning of the actuator 26 acting on the foot rest 22must be stopped.

A first test 116 determines whether the foot rest 22 is in its totallyretracted position. This first test is carried out for example from theposition of the actuator 26 supplied by the sensor 46.

If the foot rest is actually in this maximum position, stoppage of theactuator 26 is demanded during a step 118. Otherwise the test of step120 is implemented.

This test aims to determine whether or not the timing T₁ initiated atstep 112 has ended. If such is the case, the stoppage of the foot restis demanded at step 118.

On the other hand, if the timing has not come to an end, it isdetermined, at step 122, whether or not the back rest is stopped. Thisstoppage may result from a malfunctioning of the seat or from the factthat the back rest has reached its totally raised position and the backrest has been stopped at step 106 after the condition of the testcarried out at step 108 has been satisfied.

The tests of steps 116 to 122 are implemented successively in a loop aslong as one of the stoppage conditions is not satisfied.

If the back rest is actually stopped, the stoppage of the actuator 26controlling the foot rest is demanded at step 124.

After the stoppage of the foot rest, at step 118 or 124, it is redriven,at step 126, by the actuator 26 to its initially stored position, theactuator 26 being controlled in a direction opposite to its initialcontrol direction. Thus the actuator is then controlled in order tocause extraction of the foot rest.

However, before the implementation of step 126, when the foot rest isstopped at step 118, a test 127 is carried out after step 118 in orderto trigger step 126 only when the back rest 18 is actually stopped.

For this purpose, the test step 126 is effected in a loop until it isverified.

The detail of step 126 will be described with regard to the flow diagramin FIG. 3.

At the end of steps 106 and 126, the algorithm for raising up the backrest is ended at step 130.

The flow diagram given in FIG. 3 is that of the algorithm used at step126 for returning the foot rest to its initial position stored at step110.

Initially, at step 200, the actuator 26 is started up in order to causethe extension of the foot rest. Thus the actuator 26 is actuated in theopposite direction compared with the direction in which it was actuatedat step 114.

The algorithm next includes a step 202 of estimating the intensity i ofthe current consumed by the actuator 26. This intensity is supplied tothe information processing unit 40 by the monitoring means 42.

At step 204, the central information processing unit 40 collects anestimate of the drift with respect to time di/dt of the intensity of thecurrent consumed. This estimation is produced by calculating the timedrift of the intensity i supplied by the monitoring means 42.

A test is carried out at step 206 in order to compare the intensity iestimated with a threshold value I stored in the information processingunit 40.

This threshold value I is fixed experimentally and corresponds to aminimum current value consumed by the actuator 26 when the foot reststrikes an obstacle, whilst it is returning to its extended position.

If the value of the intensity i of the current supplied by themonitoring means 42 is greater than the threshold value I, a backwardreturn of the actuator over a short travel is demanded at step 208 bythe information processing unit 40 controlling the interface 38 in thisregard. The backward return is effected for example during a briefpredetermined period of time during which the motor of the actuator 26is rotated in the reverse direction.

As a variant, the backward return is effected over a brief travelpredetermined by the actuator, the control of the latter being providedby the sensor 26.

At the end of this brief backward return, at step 208, the stoppage ofthe actuator 26 is demanded at step 210, thus ending step 126 of thealgorithm illustrated in FIG. 2.

On the other hand, if, at step 206, the intensity i estimated is lessthan the predetermined threshold, a second test is carried out at step212. During this step, the value di/dt of the drift with respect to timeof the intensity i of the current consumed by the actuator 26 iscompared with a threshold value D stored in the information processingmeans 40. This threshold value D corresponds to a minimum value of thedrift with respect to time of the intensity of the current consumed bythe actuator 26 when the foot rest 22 strikes an obstacle, whilst it isbeing returned to its extended position. If the estimated value of thedrift with respect to time di/dt of the intensity of the currentconsumed is greater than the threshold value D, step 208 leading to abrief backward return of the actuator is implemented.

On the other hand, if this condition is not fulfilled, the functioningof the actuator in its direction tending to cause the extension of thefoot rest 22 is continued and step 214 is implemented. During this step,a test is carried out aimed at determining whether the foot rest 22 hasor has not reached its initial position stored at step 110.

If this initial position is not reached, the successive steps 204 to 212are once again implemented. On the other hand, if this initial positionis reached, the stoppage of the foot rest is demanded at step 210.

The return of the foot rest into its initial position is estimated bythe information processing unit from the current position of theactuator supplied by the sensor 46.

It will be understood that, with a control of the actuators as describedhere, when the back rest is controlled towards its upright position,leading to a lowering of the squab, the foot rest 22 is, concomitantlywith the movement of the back rest, moved first of all in a directionresulting in its retraction and then in an opposite direction resultingin a movement towards its extended position.

Thus, when the squab is lowered under the effect of the raising up ofthe back rest, the assembly formed by the leg rest and foot rest is notmechanically stressed whilst being pressed against the floor even if, atthe time of actuating the back rest, the foot rest is close to oralready in contact with the floor.

This solution thus makes it possible not to cause fatigue on the seatstructure and on the elements affording its actuation. On the otherhand, since the purpose of the method used is not to prevent the bottomend of the foot rest striking the floor, the foot rest can be taken intoall accessible positions. In particular, the command to return the footrest to its initial position enables it to be brought as close aspossible to the position which it occupied before the actuation of theback rest.

The method described here for the movement of the back rest and footrest can be applied for all the other elements of the seat, which,during their movement, have an influence on each other and may cause oneof the seat elements to come into contact with an obstacle.

Step 208 is optional. Thus, if one of the tests carried out at steps 206and 212 is satisfied, the stoppage of the foot rest is controlleddirectly at step 210.

As a variant, the step 110 of storing the position is eliminated and thetest of step 214 is replaced by the implementation of a second timing T₂initiated when the foot rest is started up at step 200. The duration ofthis timing is such that, according to the speed of the actuator in itstwo directions of movement, the movement travels during the periods T₁and T₂ are substantially identical.

Thus, in this variant, the timing is initiated when the actuator isstarted up at step 200 and the test carried out at step 214 verifiesthat the timing has reached its end.

According to yet another variant implementation of the method, duringthe raising of the back rest, the leg rest is raised at least partiallyin replacement for the retraction of the foot rest.

Likewise, according to yet another variant, the leg rest is partiallyraised simultaneously with the retraction of the foot rest.

In both cases, the leg rest is returned to its initial position afterthe stoppage of the back rest.

What is claimed is:
 1. A method of managing the kinematics of a seat,said seat having at least three seat elements that are able to move withrespect to each other and said seat having at least two actuatorsactuable in different directions for moving the three elements withrespect to each other, said method comprising the step of: actuating afirst actuator of said at least two actuators in one direction, saidactuating of the first actuator step always including a step ofactuating a second actuator of said at least two actuators in a givendirection and then in an opposite direction to said given direction. 2.A method according to claim 1, wherein the actuating step of the secondactuator in said given direction is effected for a first predeterminedduration.
 3. A method according to claim 2, wherein the actuating stepof the second actuator in said opposite direction is effected for asecond predetermined duration.
 4. A method according to claim 3, whereinthe first and second predetermined durations are such that, according toa speed of movement of the second actuator in the given direction and inthe opposite direction, the movement travels in both the given andopposite directions are substantially identical.
 5. A method accordingto claim 1, wherein, before the movement of the second actuator in saidgiven direction, the step of activating the second actuator includes astep of measuring and storing a current position of the second actuator,and wherein the actuating step of the second actuator in said oppositedirection is effected at most until the second actuator returns to saidstored position.
 6. A method according to claim 1, wherein the methodincludes a step of monitoring at least one variable characteristic of aforce produced by the second actuator during actuation thereof in saidopposite direction, and a step of estimating at least one predeterminedevaluation criterion relating to a characteristic variable or variables,and wherein the method includes a step of actuating the second actuatorin accordance with a predefined control instruction, ending the movementof the second actuator in the opposite direction, when at least one ofthe predetermined evaluation criteria is satisfied.
 7. A methodaccording to claim 6, wherein said predetermined control instruction isan instruction chosen from a group consisting of a stoppage of thesecond actuator and a driving of the second actuator in said givendirection.
 8. A method according to claim 6, wherein the second actuatorconsumes electric current and wherein at least one variablecharacteristic of the force produced is a variable characteristic of anelectric current consumed by the second actuator chosen from a groupconsisting of an intensity consumed by the second actuator and a driftwith respect to a time of the intensity consumed by the second actuator.9. A seat having at least three seat elements able to move with respectto each other and at least two actuators for moving the three elementswith respect to each other, wherein the seat further has means ofactuating a first actuator of said at least two actuators in onedirection and automatic means of actuating a second actuator of said atleast two actuators in a given direction and then in an oppositedirection, whenever said first actuator is actuated in said onedirection.
 10. A seat according to claim 9, further including: a movablesquab; a back rest articulated on the squab; a leg rest articulated onthe squab; a foot rest mounted so as to be able to move with respect tothe leg rest; and wherein said first actuator is adapted for a conjointmovement of the back rest and of the squab by providing a lowering ofthe squab when the back rest is raised up; and wherein the secondactuator is adapted for a movement of the foot rest with respect to theleg rest.
 11. A seat according to claim 9, further including: a movablesquab; a back rest articulated on the squab; a leg rest articulated onthe squab; and wherein said first actuator is adapted for a conjointmovement of the back rest and of the squab by providing a lowering ofthe squab when the back rest is raised up; and wherein said secondactuator is adapted for a movement of the leg rest with respect to thesquab.